Non-aqueous electrolyte primary batteries include a positive electrode including a fluorinated carbon, a negative electrode including a lithium metal, a non-aqueous electrolyte including a non-aqueous solvent in which a solute is dissolved, and a separator. Such non-aqueous electrolyte primary batteries have a high energy density.
Here, when the non-aqueous solvent includes γ-butyrolactone, batteries can maintain stable characteristics for a long period. For this reason, batteries that include a non-aqueous solvent including γ-butyrolactone are being used as the main power sources for equipment that is used over a long period (e.g., an intelligent gas meter), or back-up power sources (e.g., a memory back-up power source).
Moreover, γ-butyrolactone has a high boiling point. Therefore, batteries that include a non-aqueous solvent including γ-butyrolactone exhibit stable characteristics even under an environment with a high temperature of 100° C. or above. Non-aqueous electrolyte primary batteries having excellent high-temperature characteristics have garnered attention, for example, as the power sources for tire air pressure sensors.
However, a non-aqueous electrolyte including γ-butyrolactone has a high viscosity. Accordingly, the efficiency of the impregnating operation of electrodes or a separator with the non-aqueous electrolyte is reduced, reducing the productivity of batteries. Furthermore, when the non-aqueous electrolyte has a high viscosity, the electrolyte retention of a separator is reduced, so that it becomes difficult to realize stable discharge.
Therefore, in order to improve the productivity of batteries, a nonwoven fabric having excellent electrolyte retention is used for separators.
Further, in order to improve the electrolyte retention of a separator, it is proposed to provide hydrophilic fibers on the surface of the separator (Japanese Laid-Open Patent Publication No. Hei 5-36394). In addition, it is proposed to add a surfactant to resin fibers constituting a nonwoven fabric (Japanese Laid-Open Patent Publication No. 2000-133237).
For the fibers constituting the nonwoven fabric, polypropylene, polyphenylene sulfide, polybutylene terephthalate or the like is used.